It is known to use a photosensitive material having a transparent film on which a diazo-containing photosensitive layer capable of affording a light-shielding colored image as a photomask for the fabrication of printed wiring boards and various printing plates.
In the fabrication of a printed wiring board, a photosensitive resin layer is formed over a conductive layer such as a copper clad laminate. A photomask is superimposed on the photosensitive resin layer. Then, the photosensitive resin layer is exposed through the photomask using a contact printing device. The exposed photosensitive resin layer is developed to form a pattern. The conductive layer is then etched according to the pattern. The remaining photosensitive layer is thereafter removed to give a desired wiring pattern. The contact printing step has a great influence upon resolution of images and working efficiency in the production of printing wiring boards. In particular, when the photomask is not closely contacted with the photosensitive resin layer, Newton rings and air entrainment occur to cause cutting or distortion of wiring patterns. Thus, it is necessary to evacuate air between the photomask and the photosensitive resin layer for a long period of time in order to obtain good contact therebetween.
JP-A-H07-168306 discloses a diazo-containing photosensitive material having a transparent support, and a diazo-containing photosensitive layer provided over a surface of the support and including a binder, a diazo compound, a coupler and solid powder having an average particle diameter of 1-8 .mu.m, wherein the diazo compound is represented by the following formula: ##STR2##
(wherein R.sup.1 and R.sup.2 stand, independently from each other, for a lower alkyl group and X stands for an anionic group), and wherein the coupler comprises phenylphenol and N-(2'-hydroxyalkyl)-.beta.-resorcylamide. It has been found that a photomask obtained from the diazo-containing photosensitive material encounters a problem that the diazo-containing photosensitive layer, when contacted with a photosensitive resin layer during contact printing stage, is affected by monomers or a solvent contained in the photosensitive resin layer to cause deterioration of the durability of the diazo-containing photosensitive layer and lowering of pattern resolution. It has been also found that a surface of the diazo-containing photosensitive layer is apt be injured by frictional contact with working tables or with another diazo-containing photosensitive material during operation or storage.
U.S. Pat. No. 5,382,495 discloses a photosensitive material having an overcoat layer provided on a diazo-containing photosensitive layer so as to improve resistance to solvents and resistance to injury. When a latent image is produced on a photosensitive resin layer using a photomask obtained from the above photosensitive material, a problem of a reduction of the resolution of the image produced on the photosensitive resin layer is caused due to the presence of the overcoat layer between the photosensitive resin layer and the diazo-containing photosensitive layer. Another problem is also caused because it is very difficult to produce the diazo-containing photosensitive material.
It is an object of the present invention to provide a photosensitive material having a diazo-containing photosensitive layer, whose photosensitive layer has good resistance to solvents and to injury, which provides good contact with an original image film and with a photosensitive resin layer on a copper clad laminate layer, which is capable of affording a photomask that requires only a short period of time for removing air between the photomask and the photosensitive resin layer by suction, which gives a background (transparent portion) having good UV permeability, and which gives images having high resolution and excellent UV-shielding properties.